(a) Technical Field
The present invention relates to a power transmission device for a hybrid vehicle. More particularly, the present invention relates to a power transmission device for a hybrid vehicle capable of reducing engine vibration, facilitating engine clutch control, and providing a package layout suitable for mass production.
(b) Background Art
In general, a power transmission device for a hybrid vehicle has a layout in which an automatic transmission, a motor, an engine and an integrated starter-generator (ISG) are arranged in a row.
In the hybrid vehicle using the engine and the motor in a cooperative manner, the motor having good efficiency at a low RPM is used for initial acceleration. When the vehicle reaches a predetermined speed, the generator, i.e., the ISG starts the engine, and the outputs of the engine and the motor are used simultaneously.
At this time, in order to integrally use the output of the engine and the output of the motor, the vehicle has a structure in which each of the outputs is connected to one unit of a planetary gear of the automatic transmission.
That is, the engine is connected to a carrier of the planetary gear, the ISG is connected to a sun gear of the planetary gear, and the motor is connected to a ring gear.
Accordingly, rotational power of the engine is adjusted to an appropriate speed in the planetary gear of the automatic transmission, then transferred to a drive shaft, and finally transferred to a drive wheel through a propeller shaft.
At the same time, the ISG connected to the sun gear of the planetary gear in the automatic transmission receives the rotational power from the engine and generates electricity during deceleration. The electricity generated by the ISG is charged to a charger through an inverter, not depicted, and then the inverter supplies electricity to the motor for rotating the drive shaft during vehicle startup or acceleration.
Since the power transmission device for a hybrid vehicle has a structure in which the automatic transmission, the motor, the torque converter, the engine and the ISG are arranged in a row, the overall length of the engine room is increased, and thus it is disadvantageous in terms of the layout and mounting of the respective components. Moreover, it is difficult to commonly apply such a power transmission device to a plurality of different platforms. Accordingly, extensive research aimed at developing a power transmission device which is advantageous for mass production and has an optimal layout has continued to progress.
U.S. Pat. No. 6,176,808 discloses a layout for a power transmission for a hybrid vehicle, in which a motor is connected to an input shaft of a transmission through a torsion damper. However, such a layout has a drawback in that the positions of an engine clutch, the torsion damper and the like are complicated.
Moreover, U.S. Pat. No. 6,474,428 discloses a layout for a power transmission for a hybrid vehicle, in which a motor and an engine clutch are not disposed in a space, but partitioned by a cover. Accordingly, it has a drawback in that the motor is not immersed in oil and thus cooling efficiency is reduced.
The information disclosed in this Background section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person skilled in the art.